"There were two non-student intruders in our building this morning. They were not armed. As an extra precaution, we decided to dismiss students for the day so police have full access to the school to search it," Superintendent Melissa Jamula said.

At least one of the men was a former student and the school acted on directions by police, Jamula said. She did not know if any students had been specifically threatened.

Classes were in session at the time and the school's approximately 1,100 students were evacuated, school officials said.